The objective of this work was to test the bioactivity of the different extracts and fractions of the leaves of Plectranthus grandis and to determine their lethal concentrations on Biomphalaria glabrata. For the bioassays, seven crude extracts obtained in soxhlet extractor with organic solvents and five fractions were used by flash filtration chromatography. The bioassays were performed in 200mL glass and 24-well plates, using 1674 mollusks in the bioassays. The results showed that the 500mg/L beaker tests obtained 100% mortality rate for the crude extracts in hexane and dichloromethane and 93% for chloroform extract. In plaque tests, the dichloromethane extracts the lowest CL90 = 318mg/L. The mortality rate with the fractions was 100% at a concentration of 300mg/L. It was concluded that the tests performed on cups and plates showed significant results.